The present invention relates to a carbonaceous nanotube, nanotube aggregate, and a method for manufacturing a carbonaceous nanotube. Described in further detail, the present invention relates to a carbonaceous nanotube, nanotube aggregate, and manufacture method for a carbonaceous nanotube, having excellent conductivity and excellent wettability.
A conventional method, known as the fluidized vapor method, is recognized for the manufacture of vapor grown carbon fiber. In this method, at least one type selected from the group consisting of organic metal compounds and inorganic metal compounds, and an organic compound, and a carrier gas are transported to a reaction region heated to around 1000xc2x0 C.
In the fluidized vapor method, very small metal particles are generated in the vapor phase. The organic compounds on the metal particles suspended in the vapor phase decompose, allowing carbon to be deposited on these metal particles. By the growth in one direction of the deposited carbon, a vapor grown carbon fiber is obtained.
According to the conventional fluidized vapor method, a vapor grown carbon fiber having a constant aspect ratio with an outer perimeter diameter of 0.05 xcexcmxcx9c10 xcexcm and a length of 0.2 xcexcmxcx9c2000 xcexcm is easily manufactured industrially (M. Hatano, T. Ohsaki, K. Arakawa; 30th National SAMPE Symposium preprint 1467 (1985), Japanese Examined Patent Publication Number 62-49363).
According to the fluidized vapor method, a highly crystalline carbonaceous fiber with a diameter of 0.05xcx9c2 xcexcm (Japanese Examined Patent Publication Number 3-61768), highly crystalline carbonaceous fiber with a diameter of 0.01xcx9c0.5 xcexcm (Japanese Examined Patent Publication Number 5-36521), a vapor grown carbon fiber with a diameter of 3.5xcx9c70 nm (Japanese Examined Patent Publication Number 3-64606, Japanese Examined Patent Publication Number 3-77288), and the like, can be manufactured.
Another conventional method for the manufacture of graphite nanotubes is through arc discharge between graphite electrodes.
According to this conventional method, a plurality of graphite layers are layered from the inner perimeter surface to the outer perimeter surface. Its outer perimeter diameter is 10 nm or less, and its inner perimeter diameter is a few nanometers. A graphite nanotube which does not contain hydrogen atoms is obtained.
However, with the arc discharge method, there are several problems. For example, (a) the manufacturing method is complex because the reaction must be conducted under a vacuum or reduced pressure, and it is difficult to supply the graphite which is consumed by the arc discharge between the electrodes; (b) because the manufactured graphite nanotube is formed with graphite that does not contain hydrogen and because the manufactured graphite nanotube has few fullerene structure active sites, the chemical reactivity of the graphite nanotube is poor, (c) with the composite material obtained by combining the graphite nanotube and a resin, the mechanical strength of the composite material can not be improved because of poor wettability of the graphite nanotube with respect to the resin.
With the above highly crystalline carbon fiber (Japanese Examined Patent Publication Number 5-36521), there are also problems. The chemical reactivity is poor because the highly crystalline carbon fiber is a graphite with high crystallinity. A composite material obtained by combining the highly crystalline carbon fiber and a resin has poor wettability due to the highly crystalline nature carbon fiber. This results in a composite with poor mechanical strength which cannot be improved.
With the carbon fibers of the above highly crystalline carbon fiber (Japanese Examined Patent Publication Number 5-36521) and vapor grown carbon fibers with diameters of 3.5xcx9c70 nm (Japanese Examined Patent Publication Number 3-64606, Japanese Examined Patent Publication Number 3-77288), and the like, they are made into a more complete graphite crystal through heat treatment of the carbon fiber to make a graphitized carbon fiber. A further chemical stabilization of its surface is also performed.
With the above graphitized carbon fibers, because the graphite structure is well developed, the conductivity is very high. At the same time, because the fiber surface is chemically stable, the chemical reactivity is poor. For example, when a conductive coating material, obtained by mixing this carbon fiber and an adhesive, is coated on a coating target, there are problems of peeling of the coating film, and the like, because the affinity of the carbon fiber and the adhesive is low, or because the affinity of the carbon fiber and the coating target is low.
It is an object of the present invention is to provide a carbonaceous nanotube, nanotube aggregate, and a method for manufacturing a carbonaceous nanotube which solves the foregoing problems.
It is a further object object of the present invention to provide a carbonaceous nanotube, nanotube aggregate, and manufacture method for carbonaceous nanotube which has excellent conductivity and excellent wettability.
Briefly stated, the present invention provides a carbonaceous nanotube having a hollow part with an inner diameter of, at most, 5 nm, and a thickness part of, at most, 10 nm. The thickness part is formed of carbon atoms and hydrogen atoms, optionally containing at least one transition metal atom. Such a carbonaceous nanotube has excellent conductivity and excellent wettability.
According to an embodiment of the present invention, there is provided a carbonaceous nanotube, comprising a hollow part having an inner diameter of, at most, 5 nm, a thickness part having a thickness of, at most, 10 nm, and the thickness part being a carbon material comprising hydrogen atoms and carbon atoms.
According to another embodiment of the present invention, there is provided a fiber aggregate, comprising carbonaceous nanotubes having a hollow part having an inner diameter of, at most, 5 nm, a thickness part, comprising carbon atoms and hydrogen atoms, having a thickness of, at most, 10 nm, the carbonaceous nanotubes being present at a ratio of at least 70 weight % with respect to the fiber aggregate, hydrogen atoms at a content ratio of 0.1xcx9c1 weight % with respect to the fiber aggregate, and carbon atoms at a content ratio of at least 98.5 weight % with respect to the fiber aggregate.
According to a further embodiment of the present invention, there is provided a method for manufacturing a carbonaceous nanotube, comprising mixing a transition metal compound, containing at least one transition metal atom, a sulfur compound, containing at least one sulfur atom, an organic compound containing a hydrocarbon, and a carrier gas, to obtain a raw material mixture, supplying the raw material mixture to a reaction region maintained at a temperature of about 900xcx9c1,300xc2x0 C. inside a reaction tube, adjusting the raw material mixture supply so that the concentration of the transition metal atom in the raw material mixture is in the range from about 0.025xcx9c0.5 mol %, and the concentration of the hydrocarbon in the raw material mixture is in the range represented by (273/(T-1000))4xcx9c10((73/T-1000)) mol %, wherein T represents the absolute temperature (K) of the reaction region.
A first feature of the present invention, for solving the above objects, is a carbonaceous nanotube, comprising a hollow part, having an inner diameter of, at most, 5 nm. A thickness part, the portion with the thickness from the outer perimeter surface to the inner perimeter surface, which is, at most, 10 nm, and preferably, at most, 5 nm. This thickness part is formed of carbon material, comprising hydrogen atoms and carbon atoms.
A second feature of the present invention, for solving the above objects, is a carbonaceous nanotube of the above feature, comprising, in addition, transition metal atoms.
A third feature of the present invention, for solving the above objects, is a fiber aggregate, comprising carbonaceous nanotubes, described in the above first feature, at a ratio of at least 70 weight % with respect to the whole. Hydrogen atoms are present at a content ratio of 0.1xcx9c1 weight % with respect to the whole. Carbon atoms are present at a content ratio of at least 98.5 weight % with respect to the whole. Transition metal atoms are present at a content ratio of 0.005xcx9c1 weight % with respect to the whole.
A fourth feature of the present invention, for solving the above objects, is a method for manufacturing a carbonaceous nanotube, wherein a raw material mixture is obtained by mixing a transition metal compound which contains transition metal atoms, a sulfur compound which contains sulfur atoms, an organic compound which contains a hydrocarbon, and a carrier gas. The raw material mixture is supplied to a reaction region which is maintained at a temperature of 900xcx9c1,300xc2x0 C. inside a reaction tube. The raw material mixture is supplied so that the concentration of the transition metal atoms in the raw material mixture is in the range of 0.025xcx9c0.5 mol % and the concentration of the hydrocarbon in the raw material mixture is in the range represented by (273/(T-1000))4xcx9c10(273/(T-1000)) mol %, wherein T represents the absolute temperature (K) of the reaction region.
The above, and other objects, features, and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.